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Mount Nyiragongo is an active stratovolcano with an elevation of 3,470 meters (11, 11, 5 in). Mountains associated with the Albertine Rift. It is located within Virunga National Park, in the Democratic Republic of Congo, about 12 km (7.5 mi) north of Goma and Lake Kivu north and west of the border with Rwanda. The main crater is about two kilometers (1 mi) wide and usually contains a lava lake. The crater currently contains two separate cooled lava benches within the crater walls – one at about 3,175 m (10,417 ft) and the lower one at about 2,975 m (9,760 ft).
Nyaragongo's lava lake has sometimes been the best-known lava lake in recent history. The depth of the lava lake varies considerably. Prior to the January 1977 eruption, the maximum elevation of the lava lake was recorded to be about 3,250 m (10,660 ft) – a lake depth of about 600 m (2,000 ft). After the January 2002 eruption, a lava lake was recorded about 2,600 m (8,500 ft) or 900 m (3,000 ft) below the rim. Since then the level has gradually increased. Nyaragongo and nearby Nyamuragira are together responsible for 40% of Africa's historical volcanic eruptions.
The volcano partially overlaps two older volcanoes, Baruta and Shaheru, and is also surrounded by hundreds of smaller volcanic cinder cones from flanking eruptions.
Nyaragongo's cone consists of pyroclastics and lava flows. Nyaragongo lavas are low-silica, alkali-rich, ultramafic extrusive rocks that are essentially free of feldspars. They range from olivine-rich melilites to leucites to nephelinites, containing varying proportions of the minerals mainly nepheline, leucite, melilite, calcilite and clinopyroxene. Due to this very low silica composition, explosions occur with fluid flow in an unusual manner. While most lava flows move slowly and rarely pose a threat to human life, Nyaragongo's lava flow can run downhill at speeds of up to 100 km/h (60 mph).
Not much is known about how long the volcano has been erupting, but it has erupted at least 34 times since 1882, including several periods where activity once continued for years, often in the form of churning lava lakes in the crater. The existence of a lava lake was suspected for some time but was not scientifically confirmed until 1948. Subsequent expeditions showed that the lake fluctuated in size, depth and temperature over time.
Lava lake activity continues. As of 2020, the lake is largely confined to a broad, sloping cinder cone (about 18 meters (60 ft) high and 180 meters (600 ft) wide) at the crater floor.
1977 Between 1894 and 1977 the crater contained an active lava lake. On 10 January 1977, the walls of the crater cracked, and the lava lake erupted in less than an hour. Lava flowed up the side of the volcano at speeds of 60 km/h (37 mph) on the upper slopes, the fastest ever lava flow, inundating villages and killing at least 50 people. The villages of Kibati and Moniki, according to reports made at the time.
Within 30 minutes, the lava lake was empty, flowing north, south and west of the volcano. Nowhere else in the world do such a steep-sided stratovolcano have such a liquid lava lake. [citation needed] Nyaragongo's proximity to heavily populated areas increases its potential to cause natural disasters. The 1977 eruption raised awareness of the unique dangers posed by Nyaragongo and led to its designation in 1991 as a volcano of the decade, worthy of special study.
The 1977 eruption was triggered by the formation of a new small volcanic vent, Murara, a short distance up the slopes of Nyamuragira.
2002 explosion
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Eruptions in 1982–1983 and 1994 enhanced lava lakes in the crater. The volcano's second major eruption began on 17 January 2002, increasing seismic and fumarolic activity over several months. 13 kilometers (8.1 mi) of fissures opened on the south side of the volcano, spreading from 2,800 to 1,550 meters (9,190 to 5,090 ft) in a matter of hours.
